Compressibility effect in evaluating the pore-size distribution of kaolin clay using mercury intrusion porosimetry

The objective of the present research is to quantitatively evaluate the compression that can occur during the evaluation of pore-size distribution of cohesive soil using mercury intrusion porosimetry (MIP). A new experimental procedure was developed that can be routinely used to evaluate the corrections associated with the compressibility for porous solid samples using MIP. The approach used in this study involves performing mercury intrusion tests on dehydrated kaolin samples using freeze-dried and oven-dried techniques, and on identical samples confined by low-porosity latex membranes. Corrections for latex intrusion and issues related to dehydration of samples are addressed. The measured contact angle of mercury with kaolin clay using the sessile drop technique was used in the data reduction. Repeatable test results were obtained throughout the testing program. The procedure for obtaining volume-change behavior under isotropic conditions for a large range of pressures using the mercury porosimeter is also presented for oven-dried samples. Scanning electron micrographs for intruded and compressed specimens are presented along with a discussion on the observed hysteresis in MIP test data. The test results for kaolin samples show substantive initial compression before the occurrence of actual intrusion. This resulted in errors associated with the interpretation of pore sizes with diameters in the range of 0.4-200 µm.Key words: mercury intrusion, clay, compression, correction, pore-size distribution, high pressure.